3. Key Drivers and Technical Developments in Aviation

The aviation industry has grown strongly over the past decades at a global rate of around 5 %/a. Within the context of this rapid growth, environmental awareness of societies and general actions to mitigate global climate change have led various institutions and stakeholders to formulate and proclaim goals for limiting greenhouse gas emissions of the future global air transport fleet which are a fleet-wide efficiency improvement of 1.5 %/a from the present until 2020, a cap of CO₂ emissions from 2020 onwards by market-based measures and a halving of the global fleet’s overall CO₂ emission quantities by 2050 relative to 2005 levels. However, despite these substantial efforts to develop new or upgraded aircraft programmes in order to increase fuel efficiency, it is obvious that the target of carbon-neutral growth from 2020 onwards will not be met without market-based measures. In the long term, more radical technologies will be promoted like unconventional aircraft concepts and new engine core concepts. Also alternative energy carriers like electricity, hydrogen, or liquid natural gas are technologies with potential to reduce the environmental footprint, but typically it takes 20 years or more from conceptualisation of a new technology to operational maturity. Today, available technology improvements are outpaced by the strong growth in aviation, while future novel and more radical technologies with large CO₂ emission reduction potentials are still at very low technology readiness levels and hence far from industrial implementation. Even in the case of a rapid technology maturation, a fleet-wide penetration would require radical production ramp-ups and an aggressive industrialisation strategy for such novel technologies. To bridge the gap between the fleet-wide introduction of ultra-low emission aircraft technologies and the necessary substantial reduction of greenhouse gas emissions already today, renewable “drop-in” fuels, offering substantially smaller CO₂ footprints compared to conventional jet fuel, are considered a promising way forward.